Sarah Ann Tompkins - Obituary indicates death date of July 10, 1856

The obituary, as seen here: https://www.newspapers.com/clip/56794870/obituary-for-sarah-ann-tom...

states: At Tompkinsville, Staten Island, on Thursday, July 10, SARAH ANN, widow of the late Archibald Gordon, and daughter of the late Daniel D. Tompkins.

What is the source for the date of birth? Find a grave has the same DOB, but no photograph of the gravestone. It also corroborates the 1856, not 1853, date of death. https://www.findagrave.com/memorial/150867071/sarah-ann-gordon